Purdue News

September 2, 2004

Ticks lurk everywhere, but can be avoided

WEST LAFAYETTE, Ind. - Walks through the woods and meadows can be relaxing and even romantic, but tiny creatures that carry deadly diseases are lurking on those gently blowing leaves and waves of grass.

The danger from ticks is highest during outdoor activity in spring through summer in most regions of the world, but precautions can minimize the chances that you'll become a victim, according to a Purdue University entomologist. The two most common tick-borne diseases in the United States are Rocky Mountain spotted fever and Lyme disease, but ticks, which are neither insects nor spiders, also spread organisms that cause many other illnesses. Many of these pathogens are on the Centers for Disease Control and Prevention's Select Biological Agents and Toxins list.

"The list of diseases that ticks can transmit seems to be ever-increasing," said Catherine Hill, an entomology geneticist. "It's pretty clear that a number of the diseases they carry could be intentionally introduced pathogens."

Ticks are arthropods, meaning they have a hard outer layer, called an exoskeleton, rather than an internal skeleton, and jointed legs, but no antennae or lower jaw. They feed off blood during their larval, nymph and adult stages. These meals are needed for development during the first two stages, and in the final stage for the adult female to nourish the thousands of eggs she'll lay.

The life cycle of ticks is from a few months to two years depending on the species, of which there are about 850 worldwide. Once the tick egg hatches, it becomes a mobile six-legged larva that feeds off small rodents. The next metamorphosis is to an eight-legged nymph and then to an adult. For their meals, the nymphs and adults attach themselves to various animals such as deer, dogs, cats, reptiles, birds and people, among others.

Ticks find meals by detecting the carbon dioxide animals and people emit when they breathe. Experts also believe that heat and movement attract the arthropods. Once the blood-sucking animal finds a host, it especially likes to hide in protected, warm, humid places with hair.

"Ticks are very competent vectors of disease-causing pathogens," Hill said. "They have developed ways to feed on many types of animal hosts for long periods of time. One way to ensure that you don't contract a disease from them is to check for ticks on your body, especially if you have been in a tick-infested area. If you find any, remove them immediately."

Ticks must feed on their host for six to 10 hours to transmit Rocky Mountain spotted fever and at least 48 hours for Lyme disease, according to the CDC. Only about 1 percent of the tick species that can spread Lyme disease are infected with the bacterium.

Ways to avoid ticks and guard against the pathogens they transmit include:

• Using repellent with DEET. Always follow instructions when using these chemicals.

• Wearing light-colored long pants and long-sleeved shirts. Light-colored clothing makes it easier to spot ticks.

• Tucking bottoms of slacks into socks or wearing long boots.

• Wearing a hat to keep ticks from latching onto your scalp.

• Inspecting clothing and your body regularly if you are outside.

• Removing ticks immediately using tweezers to grab the tick as close to the skin as possible and pulling straight out. Don't twist or rotate the tick and avoid rupturing it.

• Washing your hands and the area where the tick was attached with soap and water.

• Keeping grass and brush around residences and play areas cut. Grass should be no more than 6 inches high. This lowers the humidity and raises the soil temperature, a deadly combination for ticks.

• Removing leaf, brush and woodpiles from around houses and the edge of yards.

• Using tick and flea collars, sprays and dips on pets.

Writer: Susan A. Steeves, (765) 496-7481, ssteeves@purdue.edu

Source: Catherine Hill, (765) 496-6157, hillca@purdue.edu

Ag Communications: (765) 494-2722; Beth Forbes, forbes@purdue.edu
Agriculture News Page


Related Web sites:
Purdue University Department of Entomology

Indiana State Department of Health, Tick-borne Disease

National Institutes of Health, Medline Plus

Centers for Disease Control and Prevention Division of Vector-Borne Infectious Diseases


Related release:
Identifying tick genes could halt disease, bioterrorism threat


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